The invention relates to an unstable optical resonator device comprising a spherical back mirror, a spherical outcoupling mirror, wherein a focal point lies between the back mirror and the outcoupling mirror and an optically active medium arranged between the back mirror and the outcoupling mirror.
An unstable optical resonator for an optically active medium is known from DE 10 2004 008 640 A1, which comprises a spherical back mirror and a spherical outcoupling mirror, wherein an asymmetric outcoupling in relation to the optical axis occurs.
A laser device is known from DE 43 35 585 C2, in which an outcoupling mirror is provided that has a recess or pass region on its edge, through which a laser light bundle composed of parallel laser beams reflected by a total reflection mirror can exit from the resonator.
A solid-state laser is known from GB 2 276 031 A, which has resonance means for forming an unstable negative-branch resonator in a direction of width and a stable resonator in a direction of thickness of the laser medium.
An unstable optical resonator that has a feedback reflection surface is known from U.S. Pat. No. 4,079,340.